Tests of the Standard Model and Constraints on New Physics from Measurements of Fermion-pair Production at 183 GeV at LEP

TL;DR

This paper reports precise measurements of fermion-pair production at 183 GeV at LEP, testing the Standard Model and setting limits on potential new physics like contact interactions and new heavy particles.

Contribution

It provides new experimental data at 183 GeV, compares it with Standard Model predictions, and constrains theories beyond the Standard Model involving new particles or interactions.

Findings

Measured cross-sections and asymmetries agree with Standard Model predictions.

Set limits on four-fermion contact interactions and heavy particle exchanges.

Observed the energy dependence of the electromagnetic coupling constant.

Abstract

Cross-sections for hadronic, b-bbar and lepton pair final states in e+e- collisions at sqrt(s) = 183 GeV, measured with the OPAL detector at LEP, are presented and compared with the predictions of the Standard Model. Forward-backward asymmetries for the leptonic final states have also been measured. Cross-sections and asymmetries are also presented for data recorded in 1997 at sqrt(s) = 130 and 136 GeV. The results are used to measure the energy dependence of the electromagnetic coupling constant alpha_em, and to place limits on new physics as described by four-fermion contact interactions or by the exchange of a new heavy particle such as a leptoquark, or of a squark or sneutrino in supersymmetric theories with R-parity violation.